1. Field of the Invention
The present invention relates to a method of manufacturing a blank raw material for a hose end fitting and a method of manufacturing a hose end fitting. More particularly, the present invention relates to a method of manufacturing a hose end fitting in which a hose end fitting used for a hydraulic braking device of an automobile is manufactured and a method of manufacturing a blank raw material for a hose end fitting in which a blank raw material for a hose end fitting for manufacturing this hose end fitting is manufactured.
2. Description of the Related Art
A conventional hose end fitting for a hydraulic braking device of an automobile is manufactured in accordance with the procedure shown in FIGS. 1A through 1D. First, a main body 16 is manufactured through cutting or cold forming (deformation processing) (FIG. 1A). The main body 16 is formed from a raw material and comprises a cylindrical hose press-contacting portion 10 having a bottom, a cylindrical screw connecting portion 12 having a bottom, and a flange portion 14. Next, a thread is tapped in the inner circumference of the screw connecting portion 12 using a tap to form a female screw 18 and a through-hole 22 is punched in the center of a partitioning wall 20 (FIG. 1B).
On the other hand, a nipple 24, which serves as an inner cylinder and includes a seat portion 26 connected to a flared tube, is manufactured separately from the main body 16. Then, the nipple 24 is inserted through the through-hole 22 of the main body 16 such that the nipple 24 and the through-hole 22 are assembled. The nipple 24 and the main body 16 are adhered through brazing or welding. A hose end fitting is thereby manufactured (FIGS. 1C and 1D).
FIGS. 2A through 2D show another procedure of manufacturing a conventional hose end fitting for a hydraulic braking device of an automobile. In this manufacturing procedure, a seat portion 26 and a nipple attachment hole 28 are formed at a main body 16 through cold forming, and thereafter a thread is tapped in the inner circumference of a screw connecting portion 12 to form a female screw 18 (FIGS. 2A and 2B).
In contrast, a nipple 24 in which a flange 30 is formed at the distal end is manufactured separately from the main body 16. The flange 30 of the nipple 24 is inserted through the attachment hole 28 of the main body 16 such that the nipple 24 and the main body 16 are assembled and adhered (FIGS. 2C and 2D).
When the seat portion 26 is cold forming, since the bottom of the cylindrical screw connecting portion 12 is flattened in the previous process, it is difficult to manufacture the seat portion 26. Accordingly, the raw material is annealed in a partially manufactured state so as to be completely manufactured.
However, in the conventional methods of manufacturing a hose end fitting, the nipple and the main body are assembled after being separately manufactured and are subjected to air tightness inspection in order to guarantee there is no leakage of the assembled product. Therefore, a drawback arises in that a large number of man-hours is required. Moreover, there is a drawback in that the process for manufacturing the raw material is interrupted due to the annealing process and continuous production cannot be carried out.
Because the above-described hose press-contacting portion 10 is caulked after the hose is inserted thereinto, it is required that the hardness of the hose press-contacting portion 10 is Hv 250 or less. Since the hardness of the nipple 24 needs to be Hv 120 or more so as to prevent the nipple 24 from collapsing from the caulking, the nipple and the main body are manufactured separately.